Hydraulic pump with air vent valve

ABSTRACT

A hydraulic vane pump wherein the intake opening of an air vent valve communicates with the chambers which sweep past the pump outlet and the discharge opening of the valve communicates with a channel which is provided in the pump housing for leak fluid. The valve member of the valve is held in open position by a weak spring during priming of the pump but yields and enables the valve member to seal the intake opening from the discharge opening in response to increasing fluid pressure at the outlet when the priming is completed. The body of the valve is insertable into a compartment of the housing at that axial end of the rotor which is remote from the outlet.

United States Patent Bornholt et a1.

HYDRAULIC PUMP WITH AIR VENT VALVE Inventors: Siegfried Bornholt, Lohr,Main;

Georg Schmitt, Tauberbischofsheim, both of Germany G. L. Rexroth GmbH,Lohr, Main, Germany Filed: Apr. 24, 1974 Appl. No.: 463,781

Assignee:

Foreign Application Priority Data June 1, 1973 Germany 2327814 US. Cl.417/299; 417/310; 417/435 Int. Cl. F04B 49/08 Field of Search 417/299,310, 435

References Cited UNITED STATES PATENTS 11 1950 Briggs 417/310 x 9/1966Roper 10/1967 Romcrhaus 417/299 X IIIII 7/ 1' Wk. 12d g A 2 9 \1;* 'fiiPrimary Examiner-C. .1. Husar Assistant Examiner-Leonard Smith Attorney,Agent, or FirmMichae1 S. Striker 5 7 ABSTRACT A hydraulic vane pumpwherein the intake opening of an air vent valve communicates with thechambers which sweep past the pump outlet and the discharge opening ofthe valve communicates with a channel which is provided in the pumphousing for leak fluid. The valve member of the valve is held in openposition by a weak spring during priming of the pump but yields andenables the valve member to seal the intake opening from the dischargeopening in response to increasing fluid pressure at the outlet when thepriming is completed. The body of the valve is insertable into acompartment of the housing at that axial end of the rotor which isremote from the outlet.

9 Claims, 2 Drawing Figures PATENTED AUG 2 61975 SHEET 1 BF 2 HYDRAULICPUMP WITH AIR VENT VALVE BACKGROUND OF THE INVENTION The presentinvention relates to hydraulic machines in general, especially tohydraulic pumps, and more particularly to improvements in means forpreventing a buildup of pressure at the outlet side of a hydraulic pumpduring priming.

It is already known to equip a vane pump with an air vent valve orrelief valve which connects the outlet side of the pump with theatmosphere during priming, i.e., while the chambers between the vanes ofthe rotor are being filled with oil or another hydraulic fluid. Thevalve should close in immediate response to filling of the chambers withhydraulic fluid, i.e., as soon as the priming is completed, in order toenable the pump to convey pressurized hydraulic fluid to one or moreconsumers. In presently known hydraulic pumps, the air vent valve islikely to close prior to completion of priming, for example, if theconduit which connects the outlet side with a consumer contains an elbowor bend which stores a supply of hydraulic fluid. Such fluid can causepremature closing of the air vent valve whereby the priming isinterrupted and the pump runs dry with attendant damage to moving partsand/or to the abutting surfaces between stationary and moving parts as aresult of total absence of and/or insufficient lubrication.

SUMMARY OF THE INVENTION An object of the invention is to provide ahydraulic pump, especially a vane pump, with an air vent valve whichremains open during priming of the pump, even if the conduit which isconnected to the outlet contains entrapped hydraulic fluid.

Another object of the invention is to provide an air vent value whichcan be used in existing types of hydraulic pumps.

A further object of the invention is to provide an air vent valve whichprevents damage to the pump during priming.

An additional object of the invention is to provide an air vent valvewhich occupies little room, which is of simple construction, and whichcontributes negligibly to the cost of a hydraulic pump.

The invention is embodied in a hydraulic machine, particularly in ahydraulic vane pump, which comprises a stator (this stator may include ahousing and a valve plate) having inlet means for hydraulic fluid,outlet means for pressurized fluid and channel means for leak fluid, arotor which is mounted in the stator to pressurize the fluid duringtransport from the inlet means to the outlet means, and an air ventvalve which is installed in (the housing or valve plate of) the statorand has an intake opening communicating with the outlet means, adischarge opening communicating with the cahnnel means for leak fluid,and a valve member (e.g., a sphere) which is arranged to seal the twoopenings from each other in response to increasing fluid pressure at theintake opening. Such pressure develops on completion of priming of thepump.

The air vent valve preferably constitutes a prefabricated unit, e.g., acartridge whose body contains the valve member and is insertable into acompartment of the stator.

When the invention is embodied in a vane pump, the vanes of the rotordefine with the stator a plurality of variable-volume chambers whichsweep seriatim past the inlet and outlet means of the stator. The outletmeans is preferably provided at one axial end of the rotor and the airvent valve is preferably installed in the stator at the other axial endof the rotor, and its intake opening is connected with the chamberscontaining pressurized fluid by a channel in the stator.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved pump itself, however, both as to its construction and its modeof operation, together with additional features and advantages thereof,will be best understood upon perusal of the following detaileddescription of certain specific embodiments with reference to theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a central longitudinalsectional view of a vane pump which embodies the improved air ventvalve; and

FIG. 2 is a sectional view as seen in the direction of arrows from theline 11-11 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The drawing illustrates ahydraulic vane pump including a stator having a pump housing and a valveplate 4, a rotor 3, an adjustable ring-shaped slide block 2 for thevanes 26 of the rotor 3, adjusting means for the slide block 2, and anair vent valve 12 which is installed in the stator. The housing of thestator includes a main portion 1 and a cover 7. The main portion 1(hereinafter called cup for short) has a cylindrical recess 1a whichreceives the rotor 3 with vanes 26, the slide block 2, and the valveplate 4. The slide block 2 surrounds the rotor 3 and its eccentricitywith respect to the rotor axis determines the throughput of the pump.

The inlet means of the pump includes a suction part lb, 10 which ismachined into the cup 1 at one axial end of the rotor 3 and is connectedto a source of hydraulic fluid, e.g., an oil tank, and an arcuate slot4b in the valve plate 4. The outlet means comprises a port 1d, 1e whichis machined into the cup 1 and is connected to one or more consumers,and a slot 4a in the valve plate 4. The latter is adjacent to the innersurface If of the bottom wall of the cup 1. An axial bore 1g of thisbottom wall receives a bearing sleeve 5 for the drive shaft 6 which isrotated by a motor, not shown. The cover 7 is affixed to the open end ofthe cup 1 and has a groove for a sealing ring 8 which prevents escape offluid from the chambers 27 between the vanes 26. An axial bore 7a of thecover 7 receives a bearing sleeve 9 for the stub 10 of the drive shaft6. The outer end of the bore 7a is sealed by a threaded plug 11.

The cover 7 is formed with a compartment 7b which extends radially ofthe bore 7a and receives a preassembled cartridge constituting the airvent valve 12. The body 12d of this valve has an intake opening 12a incommunication with a bore or passage 13 which is machined into the cover7 and communicates with successive chambers 27 sweeping past the outletmeans 4a, ld, 1e of the pump housing. It will be noted that the outletmeans 40, la, 1e is located at one axial end and the valve 12 is locatedat the other axial end of the rotor 3. Those chambers 27 wherein thefluid is pressurized when the rotor 3 is driven by the shaft 6 and whichcommunicate with the passage 13 are located in the portion D of thecrescentshaped space A between the slide block 2 and rotor 3.

The fluid discharging opening 12b of the body 12d of the valve 12communicates with a smaller-diameter inner end portion 7c of thecompartment 7b. The end portion 70 communicates with a radiallyextending channel 15 of the cover 7 by way of a groove 7d and a space 14between the plug 11 and the end face a of the stub 10. The channelserves for evacuation of leak fluid which flows into the space 14 fromthe space A along the internal and/or external surface of the bearingsleeve 9.

The body 12d of the valve 12 has an axial bore 12c which connects theopenings 12a, 12b and can be sealed by a spherical valve member 12e. Thelatter is biased away from its seat 12g in the body 12d by a weakhelical valve spring 12f.

The space 14 communicates with a blind axial bore 16 of the drive shaft6. The latter has a radial bore 17 which connects the axial bore 16 withan annular space 18 at the outer end of the bearing sleeve 5. The outerend of the space 18 is sealed by a packing 19.

The slide block 2 is shown in its leftmost position, as viewed in FIG.2, so that the pump conveys hydraulic fluid at a maximum rate. Theadjusting means for the slide block 2 comprises an externally threadedstop 20 in a tapped bore of the cup 1. By rotating the stop 20, theoperator can move the slide block 2 under or against the bias of astrong helical spring 21 bearing against the collar of a motiontransmitting members 22 located diametrically opposite the stop 20 andhaving a pin-shaped projection received in a socket provided in theperipheral surface of the slide block 2. The bias of the spring 21 canbe changed by a threaded retainer 23 which is in mesh with a radialextension 1A of the cup 1 and is normally concealed by a cap 23a. Asimilar cap 20a normally conceals a lock nut 20b on the shank of thestop 20.

The direction in which the rotor 3 is driven by the shaft 6 is indicatedby an arrow 24. The vanes 26 are movable in radially extending slots 25of the rotor 3 and engage the internal surface of the slide block 2under the action of centrifugal force when the shaft 6 rotates to drivethe rotor 3.

When the motor for the shaft 6 is started and the shaft 6 drives therotor 3, the volume of chambers 27 between neighboring vanes 26increases gradually in the portion S of the crescent-shaped space A,namely, while a chamber 27 travels from the locus 8, toward the locus Sshown in FIG. 2). The chambers 27 then draw fluid via inlet means lb,lc, 4b. The volume of the chambers 27 begins to decrease during travelbeyond the locus S and back toward the locus S The displaced pressurizedfluid flows through the outlet means 4a, 1e, Id and on to one or moreconsumers, not shown. The pressure of fluid in the passage 13 and intakeopening 12a of the valve body 12d is identical or nearly identical withthat in the portion 1e of the outlet means. Such pressure is amplysufficient to overcome the resis tance of the valve spring l2fand tomaintain the spherical valve member l2e in engagement with the seat 12;;of the valve body 12d so that the openings 12a, 12b are sealed from eachother and the valve 12 prevents escape of pressurized fluid from theportion D of the space A into the channel 15 for leak fluid.

However, during priming of the pump, the bias of the spring 12f issufficient to lift the valve member 12e off the seat 12;, so that thechambers 27 which sweep past the outlet means 4a, 1e, 1d of the cup 1can communicate with the channel 15 which is maintained at atmosphericpressure. This insures that the pressure in chambers 27 forming theportion D of the space A cannot rise during priming. The fluid(especially a viscous fluid, such as oil) immediately moves the valvemember 12:? against the seat 12g as soon as the priming is completedbecause the bias of the spring 12f is weak so that the openings 12a, 12bremain sealed from each other during normal operation of the pump. Thehigher the pressure of fluid in the portion D of the space A and in thepassage 13, the greater is the force with which the valve member l2e isbiased against the seat 12g. The spring 12f lifts the valve member 12 eoff the seat 12g when the shaft 6 is arrested and the pressure in theportion D of the space A decreases.

The improved pump is susceptible of many modifications without departingfrom the spirit of the invention. For example, the driven portion of theshaft 6 can be installed in the cover 7 and the air vent valve 12 can beinstalled in the cup 1 or in the valve plate 4.

An important advantage of the improved air vent valve is that itsventing action is not dependent on the orientation and/or configurationof the conduit or conduits connecting the outlet means 4a, 1e, 1d withone or more consumers. This is due to the fact that the air vent valve12 is mounted directly in the stator 1, 4, 7 of the pump so that itsoperation is not influenced by eventual accumulations of fluid in thebends, elbows or analogous portions of the aforementioned conduit orconduits.

The construction of the air vent valve in the form of a cartridge whichcan be inserted into or removed from a compartment or bore of the statorcontributes to simplicity of installation, inspection and/orreplacement. The placing of the valve at that axial end of the rotorwhich is remote from the outlet means contributes to accessibility ofthe valve and renders it possible to connect the intake opening of thevalve body with those chambers 27 which sweep past the outlet means byresorting to a relatively short passage in the stator.

Without further analysis, the foregoing will so fully revealthe gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featureswhich fairly constitute essential characteristics of the generic andspecific aspects of our contribution to the art and, therefore, suchadaptations should and are intended to be comprehended within themeaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:

1. ha hydraulic pump, particularly a vane pump, a combination comprisinga stator including housing means formed with an axial bore having aclosed end and an open end, said stator having inlet means for admissionof hydraulic fluid, and outlet means for pressurized fluid; a rotor insaid stator; shaft means coaxial with and fixed to said rotor, saidshaft means having a pair of coaxial portions respectively projecting toopposite sides of said rotor and being rotatably mounted in said axialbore, one of said portions projecting beyond the open end of said boreand the other of said portions ends short of said closed end of saidbore so as to define with said closed end a pocket for fluid leakingalong said shaft means; channel means for evacuation of leak fluid fromsaid pocket; and an air vent valve installed in said stator, said valvehaving an intake opening cummunicating with said outlet means, adischarge opening communicating with said pocket, and a valve memberarranged to seal said openings from each other in re sponse toincreasing fluid pressure at said inlet opening such as develops oncompletion of priming of the pump.

2. The combination of claim 1, wherein said valve includes a body whichis provided with said openings and contains said valve member, saidstator having a compartment for said body and being provided with firstand second passages respectively connecting said intake opening withsaid outlet means and said discharge opening with said pocket.

3. The combination of claim 1, wherein said channel means extendssubstantially radially of said rotor and is located substantiallydiametrically opposite said valve with respect to the axis of saidrotor.

4. The combination as defined in claim 1, wherein said housing meanscomprises a main body in which said rotor is located and a cover, saidinlet means and said outlet means being provided in said main body andsaid air vent valve being mounted in said cover.

5. The combination of claim 1, wherein said valve further comprises aseat between said openings and means for biasing said valve member awayfrom said seat with a force which is overcome by said valve member inresponse to a predetermined rise of fluid pressure at said intakeopening.

6. The combination of claim 5, wherein said valve member is a sphere.

7. The combination as defined in claim 1, wherein said outlet means isadjacent said one portion of said shaft means and said valve isinstalled in said stator adjacent to the other portion of said shaftmeans.

8. The combination of claim 7, wherein said stator and said rotor definea plurality of variable-volume chambers which sweep past said inlet andoutlet means in response to rotation of said rotor and said intakeopening communicates with successive chambers which sweep past saidoutlet means.

9. The combination of claim 8, wherein said stator has a passage whichconnects said intake opening with successive chambers sweeping past saidoutlet means.

1. In a hydraulic pump, particularly a vane pump, a combinationcomprising a stator including housing means formed with an axial borehaving a closed end and an open end, said stator having inlet means foradmission of hydraulic fluid, and outlet means for pressurized fluid; arotor in said stator; shaft means coaxial with and fixed to said rotor,said shaft means having a pair of coaxial portions respectivelyprojecting to opposite sides of said rotor and being rotatably mountedin said axial bore, one of said portions projecting beyond the open endof said bore and the other of said portions ends short of said closedend of said bore so as to define with said closed end a pocket for fluidleaking along said shaft means; channel means for evacuation of leakfluid from said pocket; and an air vent valve installed in said stator,said valve having an intake opening cummunicating with said outletmeans, a discharge opening communicating with said pocket, and a valvemember arranged to seal said openings from each other in response toincreasing fluid pressure at said inlet opening such as develops oncompletion of priming of the pump.
 2. The combination of claim 1,wherein said valve includes a body which is provided with said openingsand contains said valve member, said stator having a compartment forsaid body and being providEd with first and second passages respectivelyconnecting said intake opening with said outlet means and said dischargeopening with said pocket.
 3. The combination of claim 1, wherein saidchannel means extends substantially radially of said rotor and islocated substantially diametrically opposite said valve with respect tothe axis of said rotor.
 4. The combination as defined in claim 1,wherein said housing means comprises a main body in which said rotor islocated and a cover, said inlet means and said outlet means beingprovided in said main body and said air vent valve being mounted in saidcover.
 5. The combination of claim 1, wherein said valve furthercomprises a seat between said openings and means for biasing said valvemember away from said seat with a force which is overcome by said valvemember in response to a predetermined rise of fluid pressure at saidintake opening.
 6. The combination of claim 5, wherein said valve memberis a sphere.
 7. The combination as defined in claim 1, wherein saidoutlet means is adjacent said one portion of said shaft means and saidvalve is installed in said stator adjacent to the other portion of saidshaft means.
 8. The combination of claim 7, wherein said stator and saidrotor define a plurality of variable-volume chambers which sweep pastsaid inlet and outlet means in response to rotation of said rotor andsaid intake opening communicates with successive chambers which sweeppast said outlet means.
 9. The combination of claim 8, wherein saidstator has a passage which connects said intake opening with successivechambers sweeping past said outlet means.